1. Field of the Invention
The present invention relates to a numerical controller and particularly relates to a numerical controller that carries out overlapping in operation based on table format data.
2. Description of the Related Art
As a method of controlling drive of each control axis individually in synchronization with motion of a reference axis, an operation function based on table format data is well known in which position information on the control axes is stored in association with a reference axis position in the table format data provided in a memory or the like and in which each control axis is operated in synchronization with the reference axis based on the information stored in the table format data. In the function, the table format data in which time, axis positions, or axis positions based on spindle position, or auxiliary functions such as M code are set is stored in the memory or a storage device connected with a network, and the axes and the auxiliary functions are controlled while the table format data is read sequentially.
Japanese Patent Application Laid-Open No. 59-177604 and Japanese Patent Application Laid-Open No. 2003-303005 disclose numerical controllers that exercise so-called path table operation function or electronic cam control utilizing the operation function based on the table format data. These techniques enable free tool operations not restricted by machining programs and thereby attain shortening of machining time, increase in machining accuracy, and the like.
In the prior art operation based on the table format data, reference values described in the table format data and coordinate values, corresponding to the reference values, of an axis or a spindle are set as control points and a travel is calculated based on two control points set as a start point and an end point. Specifically, from the reference value and the coordinate value of the axis or the spindle at the control point that is the start point and the reference value and the coordinate value of the axis or the spindle at the control point that is the end point, a difference between the reference values of the two points and a difference between the coordinate values of the axis or the spindle at the two points are calculated and the travel per unit reference value is calculated from the differences.
FIG. 11 illustrates an example of prior art axis control using the table format data. The table format data <TIME_TABLE_0101_X> is table format data for control over an X axis based on time. L denotes the reference value (reference time: in msec) and X denotes the coordinate value (in mm) of the X axis that corresponds to the reference value. With the current reference value set as 1000 msec, the X axis moves between the two control points that are the start point with the reference value of 1000 msec and the coordinate value of 100.0 mm and the end point with the reference value of 2000 msec and the coordinate value of 200.0 mm.
FIG. 12 illustrates a schematic block diagram on a numerical controller for calculation of the travel. The numerical controller 1 illustrated in FIG. 12 notifies a distribution processing unit 11x of command blocks, sequentially read out by a readout unit, as the two control points, that is, the start point and the end point, finds the travel per unit reference value from the differences in the reference value and the coordinate value between the two control points by the distribution processing unit 11x, and notifies a motor control unit of the travel. In FIG. 12, illustration of the readout unit for the command blocks and the motor control unit is omitted.
In the distribution processing unit 11x, in the example of the X axis control using the table format data <TIME_TABLE_0101_X> having the start point with the reference value of 1000 msec and the coordinate value of 100.0 mm and the end point with the reference value of 2000 msec and the coordinate value of 200.0 mm, the travel per unit reference value is calculated at 0.1 mm/1 msec from the difference in the reference value of 1000 msec (2000 msec-1000 msec) and the difference in the coordinate value of 100.0 mm (200.0 mm-100.0 mm).
In practice, however, it is necessary to insert acceleration/deceleration commands after and/or before start/end of an operation of the axis in order to relax impact that is caused by acute velocity change. Japanese Patent Application Laid-Open No. 2007-304714 discloses a technique of controlling acceleration/deceleration by connection through quadratic/cubic function in operation based on table format data. With application of the technique of Japanese Patent Application Laid-Open No. 2007-304714, the axis control is carried out based on the table format data illustrated in FIG. 13.
Description on the commands in acceleration/deceleration sections on occasions of the start/end of the operation of the axis will be omitted below for simplification.
FIG. 13 is an example of the axis control using the table format data for only the X axis. In general, however, movement of tool holders, a work mounting table, and the like is controlled by independent operation of a plurality of axes in synchronization with the reference value.
FIG. 14 illustrates an example in which a tool is controlled with use of table format data for the X axis and a Z axis. In the operation based on table format data, each axis is independently operated in synchronization with the reference value. FIG. 15 illustrates a schematic block diagram on a numerical controller that controls a tool with use of the table format data <TIME_TABLE_0101_X> and <TIME_TABLE_0101_Z> illustrated in FIG. 14. In FIG. 15, distribution processing with the current reference value being between L1000 and L2000 is illustrated.
In consideration of shortening of cycle time of the operation based on the table format data illustrated as the prior art technique in FIG. 14, in corner parts such as L2000 where a synthesized velocity falls, it is necessary to make commands before and after the corners overlap by advancing start timing for the commands just after the corner parts. FIG. 16 illustrates an overlapping operation of the X axis and the Z axis between L1900 and L2000 in the operation based on the table format data illustrated in FIG. 14. By the overlapping of the X axis and the Z axis, as illustrated in FIG. 16, the cycle time is shortened by 100 ms subjected to the overlapping.
In the operation based on the table format data, however, a direction of travel, the synthesized velocity, and/or the like of a tool can only be calculated when a plurality of table format data are analyzed in parallel and thus it has been difficult for an operator to manually search for sites permitting the overlapping or to manually adjust overlap quantity by analyzing the table format data outputted from CAM. In performance of such a task, accordingly, it has been necessary to prepare CAM supporting the overlapping of the table format data and to output afresh the table format data from the CAM each time the overlapping sites, the overlap quantity, or the like is changed and working therefor has cost the operator labor.